In order to decrease vehicular accidents caused by drivers inadvertently drifting out of the proper lane, the use of rumble strips has become commonplace. It is especially true along vast stretches of open freeway that rumble strips help to warn drivers if they mistakenly leave their lane and enter the shoulder of the roadway. The accidental drifting off of the roadway may be caused by a variety of factors, including poor weather conditions, distracted driving, and fatigue. When vehicle tires encounter the rumble strip, both a vibration and sound stimulus alert the driver to the error, but without a good frame of reference during night driving, an accident may still occur.
The sound of a vehicle's tire traveling over a rumble strip produces a distinct complex audio waveform. With this invention, the waveform has been electronically analyzed and the corresponding ratios of voltage levels, with respect to time, have been identified that are specific within the soundwave cycle of that of a vehicle tire traveling over a rumble strip. This information is used as a reference for which a comparing circuit is responsive and leads to activation of a roadside marking device. In the prior art, a microphone was adapted to respond to the general frequency range of the sound, but this brought about inaccuracies (i.e., falsely identifying the sound of engines or other typical traffic noise falling into that audio range). This invention overcomes the limitations in previous rumble strip audio responsive systems by using sound recognition technology to identify specific sound characteristics which then can trigger a roadside warning indicator. For even higher reliability, the comparing circuit also looks for repetitive triggering waveforms before activating a warning. Additionally, this device not only warns the errant driver of the vehicle drifting out of lane, but the roadside marker warning is visible to other drivers along the roadway and alerts them of the hazardous situation. With the embodiments of this invention containing a receiver/transmitter, networking amongst numerous roadside markers is also possible which can enhance the visibility of the warning indication by propagating it to adjacent markers placed along the roadway. The networking capability of this invention to relay information has additional safety benefits as well. By adjusting the comparing circuit's responsiveness, embodiments of this invention can visually alert drivers to other unsafe conditions, such as the presence of construction work zones, and assist in general navigation by providing roadway marking and illumination.